In the context of the present invention, the term “non-precision approach” is understood to be an approach which is not a precision instrument approach, such as for example an ILS (Instrument Landing System) type approach. It is known that, in order to use a precision instrument approach, ground stations are used which are located at the edge of the runway and at least one special radio receiver installed in the aircraft, which provides horizontal and vertical guidance before and during the landing by showing the pilot the lateral deviation with respect to an approach path and the vertical deviation with respect to a descent plan. Such a precision instrument approach provides great and effective assistance in landing (by lateral guidance and vertical guidance), particularly in poor visibility (fog, etc) or when there is no visibility.
A non-precision approach, such as considered in the present invention, therefore exists when the preceding items of information are totally or partially unavailable, such that a normal precision approach cannot be implemented.
In such a non-precision approach, the pilot of the aircraft must gather a plurality of items of information relating to the performance of the aircraft's navigation equipment (computers etc.) and to the integrity and precision of measurements of particular parameters, such as the position and altitude of the aircraft for example. The pilot must mentally synthesize all of this information and choose, for the landing, between:                one of a plurality of possible assisted approach modes, for which the aircraft is provided with known means making it possible:                    to determine a virtual approach path, in particular on the basis of information contained in a database installed in the aircraft;            to calculate the lateral and vertical deviations of the aircraft's position with respect to that virtual approach path; and            to present these deviations to the pilot.                        The aircraft is then piloted in such a way as to cancel these deviations; and        a selected approach mode, for which the pilot enters descent instructions (slope, heading, etc.,) into an automatic pilot which carries out the piloting of the aircraft.        
However, this obligatory mental synthesis of the various items of information increases the workload of the pilot and constitutes a significant loss of time, whilst the pilot already has to carry out many tasks at that same time for the purpose of the landing (management of communications with air traffic control, etc.).
Furthermore, the man/machine interface is different between the approach modes of an instrument approach and the approach modes of a non-precision approach, which in particular has the disadvantage of making the ergonomics of the piloting position complex.